Peroxides from ozonides

Expls may be classified both from the chemical point of view and according to their uses. From the chemical viewpoint we distinguish between chemical individual substances and mixts. The former are divided into (1) nitro compds, (2) nitric esters, (3) nitramines, (4) derivatives of chloric and perchloric acids, (5) azides, and (6) various compds capable of pro-during an expln, for example fulminates, acetyl-ides, nitrogen rich compds such as tetrazene, peroxides and ozonides, etc... 

Dichloroaluminium hydride in ether or sodium borohydride in TEA can lead to formation of ethers from ozonides by reductive cleavage of the two C—O bonds of the peroxide bridge (Equation (19)) <85JOC275>. 

Peroxides can be obtained from ozonides in various ways. Dioxirane (246), the simplest cyclic peroxide, appears in the microwave spectrum of ethylene-ozone mixtures, in the — 115 to — 110 °C temperature range, probably as a decomposition product of the primary... 

Hydrogen atoms in allylic position are favorite sites for hydroperoxidation of chains. So, this mechanism proceeds in the formation of lateral hydroperoxides, and not like for other polymers, in intramolecular peroxides. Rearrangement of chemical structures coming from ozonides are rapidly observed (Scheme 33). 

One process (16) subjects them to light from a neon lamp ranging from yellow to orange in color, in the presence of oxygen. Another (20) subjects them to ultra-violet rays after addition of a small amount of hydrogen peroxide, inorganic and organic peroxide, or ozonide. 

The oxidative workup used to produce acids from ozonides such as 349 uses reagents such as hydrogen peroxide, peroxy acids, silver oxide, chromic acid or permanganate. The conversion of cyclohexene to adipic acid by treatment with (1) O3 and (2) H2O2 is a simple example of a typical oxidative workup. When the ozonide is disubstituted (two carbon groups on the initial carbon of the alkene), the product is a ketone and... 

The oxygen-oxygen bonds of peroxides and ozonides (resulting from the ozonolysis of alkenes) can easily be cleaved under Pd-catalyzed hydrogenation conditions (Scheme 121).[18shi90]... 

Ozonolysis of double bonds as a route to ketones and aldehydes is well known. Thiourea may be used for the reduction of the ozonide to afford aldehydes from suitable alkenes. Electrolytic reduction of ozonization products from the oxidation of trisubstituted cyclic alkenes in acetic acid offers a route to hydroxy-ketones. a-Alkoxy-peroxides, from ozonolysis in alcoholic solution, are stable... 

Aldehydes are easily oxidized to carboxylic acids under conditions of ozonide hydroly SIS When one wishes to isolate the aldehyde itself a reducing agent such as zinc is included during the hydrolysis step Zinc reduces the ozonide and reacts with any oxi dants present (excess ozone and hydrogen peroxide) to prevent them from oxidizing any aldehyde formed An alternative more modem technique follows ozone treatment of the alkene m methanol with reduction by dimethyl sulfide (CH3SCH3)... 

Due to the retractive forces in stretched mbber, the aldehyde and zwitterion fragments are separated at the molecular-relaxation rate. Therefore, the ozonides and peroxides form at sites remote from the initial cleavage, and underlying mbber chains are exposed to ozone. These unstable ozonides and polymeric peroxides cleave to a variety of oxygenated products, such as acids, esters, ketones, and aldehydes, and also expose new mbber chains to the effects of ozone. The net result is that when mbber chains are cleaved, they retract in the direction of the stress and expose underlying unsaturation. Continuation of this process results in the formation of the characteristic ozone cracks. It should be noted that in the case of butadiene mbbers a small amount of cross-linking occurs during ozonation. This is considered to be due to the reaction between the biradical of the carbonyl oxide and the double bonds of the butadiene mbber [47]. 

This discussion of the structures of diene polymers would be incomplete without reference to the important contributions which have accrued from applications of the ozone degradation method. An important feature of the structure which lies beyond the province of spectral measurements, namely, the orientation of successive units in the chain, is amenable to elucidation by identification of the products of ozone cleavage. The early experiments of Harries on the determination of the structures of natural rubber, gutta-percha, and synthetic diene polymers through the use of this method are classics in polymer structure determination. On hydrolysis of the ozonide of natural rubber, perferably in the presence of hydrogen peroxide, carbon atoms which were doubly bonded prior to formation of the ozonide... 

O NMR resonances for several 1,2,4-trioxolanes have been reported <91CC816> (Table 6). The ether and peroxide signals are very distinct proving the value of O NMR as an analytical tool for characterization of ozonides. It can be used to determine unequivocally whether a compound is an ozonide (peroxide 6 295-327 ppm) or tetroxane ((26), for example d = 256 ppm). This is often a competing product from the ozonolysis reaction of alkenes (Section 4.16.8.2). 

Section II covers the synthesis of the cyclic peroxides with medium ring size from 5 to 7. Section HI covers the synthesis of 1,2,4-trioxanes. Classification in sub-sections and sub-sub-sections is done according to the type of reaction by which the cyclic peroxide system is formed. Syntheses of dioxirans, 1,2-dioxetanes, trioxolanes (ozonides), tetrox-anes, and macrocyclic peroxides are not discussed in this review. 

Procedures. Chromatographic Purification of Ozonization Products. Ozonization products from ethyl 10-undecenoate and 1-octene were chromatographed on silica gel columns (Baker) and eluted with 15 or 25% ether in petroleum ether (b.p., 30°-60°). Fractions were examined by thin-layer chromatography (TLC) on silica gel G Chroma-gram sheet eluted with 40% ether in petroleum ether. For development of ozonide and peroxide spots, 3% KI in 1% aqueous acetic acid spray was better than iodine. The spots (of iodine) faded, but a permanent record was made by Xerox copying. Color of die spots varied from light brown (ozonide) to purple-brown (hydroperoxide), and the rate of development of this color was related to structure (diperoxide > hydroperoxide > ozonide). 2,4-Dinitrophenylhydrazine spray revealed aldehyde spots and also reacted with ozonides and hydroperoxides. Fractions were evaporated at room temperature or below in a rotary evaporator. 

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